1. Field of the Invention
The present invention relates to enhanced oil recovery systems, and particularly to a hybrid solar thermal enhanced oil recovery system with oxy-fuel combustor that uses solar thermal enhanced oil recovery in the daytime and uses an oxy-fuel combustor for fluid injection in the nighttime.
2. Description of the Related Art
Solar thermal enhanced oil recovery is a form of thermal enhanced oil recovery (EOR), a technique that is applied by oil producers to extract more oil from maturing oil fields. Solar EOR uses solar arrays to concentrate the sun's energy to heat water and generate steam. The steam is injected into an oil reservoir to reduce the viscosity and thin heavy crude oil, thus facilitating its flow to the surface. Thermal recovery processes, also known as “steam injection”, have traditionally burned natural gas to produce steam, generating environmental concerns due to the related carbon dioxide emissions. Solar EOR has recently proved to be a viable alternative to gas-fired steam production for the oil industry. Solar EOR can generate the same quality steam as natural gas, reaching temperatures up to 400° C. and 2,500 PSI.
FIG. 2 illustrates a typical prior art solar thermal enhanced oil recovery system 100, including an oil field 102, a solar power tower 104, a boiler 106, and a flow control device 108. The oil field 102 includes an oil well 110, a steam pipe 116, and an oil and water pipe 122. The system 100 further includes an oil and water separator 126, a water treatment device 112, and a feed pump 114.
In operation, the oil field 102 receives steam 118 from the flow control device 108. The steam 118 is injected into the oil well 110 of the oil field 102 through the steam pipe 116, where the steam 118 is used for extracting crude oil 120 from geologic formations 121. The injected steam 118 increases the mobility of crude oil 120 within the geologic formations 121 and eventually condenses to form a mixture of oil and water 124. The mixture of oil and water 124 is influenced by the steam and migrates towards the oil and water pipe 122, through which it is extracted from the oil field 102. Further, the mixture of oil and water 124 is fed to the oil and water separator 126 for separating extracted oil 128 from the mixture of oil and water 124, producing untreated water 129. The water treatment device 112 receives the untreated water 129 from the oil and water separator 126, where the water treatment device 112 purifies the untreated water 129 to obtain treated water 130. The treated water 130 has a low percentage of solids, sludge and salts. A first portion 130a of the treated water 130 is fed to the solar power tower 104 via a feed pump 114, and a second portion 130b of the treated water 130 is fed to the boiler 106 via the feed pump 114.
The first portion 130a of the treated water 130, which is fed to the solar power tower 104, is heated thereby, using solar radiation, thus generating a first source of steam 118a. Similarly, the second portion 130b of the treated water 130 is fed to the boiler 106 where the boiler 106 is used to heat the second portion 130b of the treated water 130 using external energy, thus generating second source of steam 118b. The flow control device 108 receives at least one of the first steam 118a from the solar power tower 104 and the second steam 118b from the boiler 106. Further, the flow control device 108 injects the received first steam 118a and the second steam 118b to the oil well 110 of the oil field 102 for extracting the mixture of oil and water 124. One such typical prior art system is shown in U.S. Patent Application Publication No. 2014/0318792, which is hereby incorporated by reference in its entirety. Such systems, however, not only require a great deal of natural gas and water to operate, but are also considerable sources of pollution and contamination for the environment, as well as being inefficient for carbon dioxide-based enhanced oil recovery. Specifically, such systems make use of conventional combustion, which emits carbon dioxide in such a way that it is difficult to separate the carbon dioxide from the nitrogen in the system, thus making it difficult to use the carbon dioxide for enhanced oil recovery. Further, such systems also emit nitrogen oxides into the environment, which are a major source of pollution.
Thus, a hybrid solar thermal enhanced oil recovery system with an oxy-fuel combustor addressing the aforementioned problems is desired.